U.S. patent number 5,699,073 [Application Number 08/610,501] was granted by the patent office on 1997-12-16 for integrated electro-optical package with carrier ring and method of fabrication.
This patent grant is currently assigned to Motorola. Invention is credited to Michael S. Lebby, Fred V. Richard, John W. Stafford.
United States Patent |
5,699,073 |
Lebby , et al. |
December 16, 1997 |
Integrated electro-optical package with carrier ring and method of
fabrication
Abstract
An integrated electro-optical package (40) including an
optically transparent substrate (10) with an array (15) of light
emitting devices (LEDs) (12) formed thereon, cooperating to
generate a complete image, thereby forming a LED display chip (14).
The LEDs (12) are positioned in rows and columns and having
electrical connections adjacent outer edges of the substrate (10).
A driver board (30), having embedded electrical conductors (34),
plated through-hole vias (44) and/or embedded leadframes (45) for
cooperating with the LEDs (12) of the LED display chip (14) and
further having a plurality of driver and control circuits (42)
connected to the driver board (30) and LEDs (12). A molded carrier
ring (50), electrically interfaced with the driver board (30), the
LED display chip (14) and the driver and control circuits (42). A
molded refractive or diffractive lens (60) positioned in alignment
with the array (15) of LEDs (12) of the LED display chip (14) and
on a side opposite the mounting of the LED display chip (14),
thereby capable of magnifying the image and producing an easily
viewable virtual image.
Inventors: |
Lebby; Michael S. (Apache
Junction, AZ), Richard; Fred V. (Scottsdale, AZ),
Stafford; John W. (Phoenix, AZ) |
Assignee: |
Motorola (Schaumburg,
IL)
|
Family
ID: |
24445267 |
Appl.
No.: |
08/610,501 |
Filed: |
March 4, 1996 |
Current U.S.
Class: |
345/82;
348/E5.027; 345/205; 313/500; 438/28; 257/99; 438/27;
257/E25.032 |
Current CPC
Class: |
H01L
25/167 (20130101); H04N 5/2253 (20130101); H01L
2224/48091 (20130101); H01L 2224/48227 (20130101); H01L
2924/12044 (20130101); H01L 2924/00011 (20130101); H01L
2224/48091 (20130101); H01L 2924/00014 (20130101); H01L
2924/12044 (20130101); H01L 2924/00 (20130101); H01L
2924/00011 (20130101); H01L 2924/01015 (20130101); H01L
2924/00011 (20130101); H01L 2924/01052 (20130101) |
Current International
Class: |
H01L
25/16 (20060101); H04N 5/225 (20060101); G09G
003/32 () |
Field of
Search: |
;345/82,83,39,46,205,206,903,905 ;348/801,802
;313/500,502,504,505,510 ;257/79,81,88,99 ;349/11,56,149-152
;437/209,211,210 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Saras; Steven
Attorney, Agent or Firm: Parsons; Eugene A.
Claims
What is claimed is:
1. An integrated electro-optical package comprising:
an optically transparent substrate with an array of light emitting
devices formed thereon and cooperating to generate a complete
image, the array of light emitting devices being positioned in rows
and columns to define all pixels of the complete image and operably
connected to a plurality of connection pads adjacent outer edges of
the optically transparent substrate;
a driver board, having defined therein a central opening,
substantially coextensive with the complete image generated by the
array of light emitting devices, a first plurality of connection
pads formed on a surface surrounding the central opening, and a
second plurality of connection pads formed on a surface about a
periphery of the driver board, the first plurality of connection
pads and the second plurality of connection pads having a plurality
of electrical conductors extending therebetween, the plurality of
connection pads of the array of light emitting devices being bump
bonded to the first plurality of connection pads of the driver
board; and
a molded carrier ring, having embedded therein, a plurality of
leadframes, electrically interfaced with and supporting the driver
board, and further having a plurality of external electrical
connections.
2. An integrated electro-optical package as claimed in claim 1
wherein the optically transparent substrate is formed of optically
transparent glass.
3. An integrated electro-optical package as claimed in claim 1
wherein the driver board is a printed circuit board.
4. An integrated electro-optical package as claimed in claim 1
wherein the plurality of electrical conductors extending between
the first plurality of connection pads and the second plurality of
connection pads formed on the driver board are at least one of a
plurality of surface mounted leadframes and a plurality of
patterned electrical interconnects.
5. An integrated electro-optical package as claimed in claim 1
including a plurality of driver circuits positioned on the driver
board and connected to the array of light emitting devices through
the plurality of connection pads of the driver board and the
plurality of connection pads of the optically transparent
substrate.
6. An integrated electro-optical package as claimed in claim 5
wherein the driver board has provided therein, a plurality of
electrical conductors, electrically connecting the first plurality
of connection pads formed on the driver board with the plurality of
driver circuits.
7. An integrated electro-optical package as claimed in claim 6
wherein the plurality of electrical conductors electrically connect
the first plurality of connection pads and the second plurality of
connection pads formed on the driver board and the plurality of
driver circuits include one of a plurality of embedded leadframes
and a plurality of plated through-hole vias.
8. An integrated electro-optical package as claimed in claim 1
wherein the driver board has positioned thereon a major surface, a
molded lens, coextensive with the complete image generated by the
array of light emitting devices to receive and magnify the complete
image and produce an easily viewable virtual image.
9. An integrated electro-optical package as claimed in claim 1
wherein the molded carrier ring has monolithically formed a
plurality of structural arms projecting from a peripheral ring
structure, toward a central area of the molded carrier ring.
10. An integrated electro-optical package as claimed in claim 9
wherein the plurality of structural arms define within the central
area, an opening into which a molded lens is positioned,
coextensive with the complete image generated by the array of light
emitting devices to receive and magnify the complete image and
produce an easily viewable virtual image.
11. An integrated electro-optical package as claimed in claim 9
wherein the molded carrier ring further has monolithically formed
within the central area, a molded lens, coextensive with the
complete image generated by the array of light emitting devices to
receive and magnify the complete image and produce an easily
viewable virtual image.
12. An integrated electro-optical package as claimed in claim 1
wherein the array of light emitting devices includes a plurality of
organic electroluminescent elements.
13. An integrated electro-optical package as claimed in claim 12
wherein the plurality of organic electroluminescent elements each
include a first conductive layer positioned on a major surface of
the optically transparent substrate, at least one layer of organic
material positioned on the first conductive layer, and a second
conductive layer positioned on the at least one layer of organic
material.
14. An integrated electro-optical package as claimed in claim 13
wherein the first conductive layer on the major surface of the
optically transparent substrate includes a layer of indium-tin
oxide.
15. An integrated electro-optical package as claimed in claim 13
wherein the at least one layer of organic material on the first
conductive layer includes one of a layer of polymer and a layer of
low molecular weight organic compound.
16. An integrated electro-optical package comprising:
a light emitting device display chip comprised of an optically
transparent substrate having a major surface with an array of light
emitting devices formed on the major surface at a central portion
thereof and cooperating to generate a complete image, each of the
light emitting devices having a first electrode and a second
electrode for activating the light emitting devices and having a
plurality of electrical conductors formed on the major surface of
the optically transparent substrate, the light emitting device
display chip further having a plurality of external connection pads
adjacent outer edges thereof and outside of the central portion of
the major surface with the first electrode of each of the light
emitting devices being connected to a first plurality of the
external connection pads and the second electrode of each of the
light emitting devices being connected to a second plurality of the
external connection pads;
a driver board having a first major surface and a second opposed
major surface and defining a central opening through the first and
second opposed major surfaces, the driver board further having a
first plurality of electrical conductors formed therein, extending
from a plurality of connection pads adjacent an edge of the central
opening on the second opposed major surface to a plurality of
connection pads located about a periphery of the second opposed
major surface of the driver board, and a second plurality of
electrical conductors formed therein, extending from the plurality
of connection pads located about the periphery of the second
opposed major surface of the driver board, to a plurality of
connection pads formed on the first major surface of the driver
board, the major surface of the optically transparent substrate
being mounted on the second opposed major surface of the driver
board with the first plurality of the external connection pads and
the second plurality of external connection pads of the optically
transparent substrate being in electrical contact with the
plurality of connection pads adjacent an edge of the central
opening on the second opposed major surface of the driver
board;
a plurality of driver and controller circuits mounted on the first
major surface of the driver board and having a plurality of data
input terminals and further having a plurality of control signal
output terminals connected to the first and second electrodes of
the light emitting devices through the first plurality of
electrical conductors, the second plurality of electrical
conductors and the plurality of connection pads of the driver
board, and the plurality of connection pads of the optically
transparent substrate, for activating the light emitting devices to
generate images in accordance with a plurality of data signals
applied to the plurality of data input terminals; and
a molded carrier ring, electrically interfaced with and supporting
the driver board, the light emitting device display chip and the
plurality of driver and controller circuits, having a plurality of
external connections formed therein.
17. An integrated electro-optical package as claimed in claim 16
wherein the optically transparent substrate is formed of optically
transparent glass.
18. An integrated electro-optical package as claimed in claim 16
wherein the first plurality of electrical conductors and the second
plurality of electrical conductors of the driver board include at
least one of a plurality of partially embedded pattern electrical
interconnects, a plurality of embedded leadframes, a plurality of
surface mounted leadframes and a plurality of plated through-hole
vias.
19. An integrated electro-optical package as claimed in claim 16
wherein the plurality of driver circuits on the first major surface
of the driver board and the light emitting device display chip are
electrically interfaced with one of wire bonding or bump
bonding.
20. An integrated electro-optical package as claimed in claim 16
wherein the array of light emitting devices includes a plurality of
organic electroluminescent elements.
21. An integrated electro-optical package as claimed in claim 16
wherein the plurality of electrical conductors formed on the major
surface of the optically transparent substrate are positioned to
fan out from the array of light emitting devices to the plurality
of connection pads formed on the major surface of the optically
transparent substrate, the first plurality of the external
connection pads and the second plurality of the external connection
pads on the major surface of the optically transparent substrate
being positioned in rows and columns on the major surface
thereof.
22. An integrated electro-optical package as claimed in claim 16
further including a molded lens, positioned coextensive with the
complete image generated by the array of light emitting devices to
receive and magnify the complete image and produce an easily
viewable virtual image.
23. An integrated electro-optical package as claimed in claim 22
wherein the molded lens is fixedly attached to the central opening
of the driver board.
24. An integrated electro-optical package as claimed in claim 22
wherein the molded lens is fixedly attached to the molded carrier
ring.
25. An integrated electro-optical package as claimed in claim 22
wherein the molded lens is monolithically formed with the molded
carrier ring.
26. An integrated electro-optical package comprising:
an optically transparent substrate having a major surface with a
plurality of light emitting devices formed on the major surface,
each of the light emitting devices having a first electrode and a
second electrode for activating the light emitting devices, the
light emitting devices defining a plurality of pixels positioned in
rows and columns and cooperating to generate a complete image, when
activated, at a central portion of the major surface, the optically
transparent substrate further having a plurality of external
connection pads adjacent outer edges thereof and outside of the
central portion of the major surface with the first electrode of
each of the light emitting devices being connected to a first
plurality of the external connection pads defining rows of pixels
and the second electrode of each of the light emitting devices
being connected to a second plurality of the external connection
pads defining columns of pixels;
a driver board having defined therein a central opening and having
a first major surface and a second opposed major surface, a first
and a second plurality of electrical connections formed on the
second opposed major surface and a plurality of electrical
interconnects formed between the first and the second plurality of
electrical connections, a plurality of electrical connections
formed on the first major surface of the driver board and a
plurality of electrical interconnects formed in the driver board
between the second plurality of electrical connections formed on
the second opposed major surface and the plurality of electrical
connections formed on the first major surface, the optically
transparent substrate being mounted on the second opposed major
surface of the driver board with the first plurality of electrical
connections of the driver board in electrical contact with the
first plurality of the external connection pads and the second
plurality of external connection pads on the optically transparent
substrate;
a plurality of driver and controller circuits mounted on the first
major surface of the driver board, having a plurality of data input
terminals and further having a plurality of control signal output
terminals adapted to be connected to the first and second
electrodes of the light emitting devices for activating the light
emitting devices to generate the complete image in accordance with
a plurality of data signals applied to the plurality of data input
terminals;
a lens, positioned substantially coextensive with the complete
image generated by the plurality of light emitting devices to
receive and magnify the complete image and produce an easily
viewable virtual image; and
a molded carrier ring, electrically interfaced with and supporting
the driver board, the plurality of light emitting devices and the
plurality of driver and controller circuits, having a plurality of
external electrical connections formed therein.
27. An integrated electro-optical package as claimed in claim 26
wherein the lens positioned substantially coextensive with the
complete image generated by the plurality of light emitting devices
to receive and magnify the complete image and produce an easily
viewable virtual image is one of a diffractive lens and a
refractive lens.
28. An integrated electro-optical package as claimed in claim 26
wherein the molded carrier ring further includes a plurality of
monolithically formed structural arms, extending from an outer
periphery of the molded carrier ring to a central area.
29. An integrated electro-optical package as claimed in claim 28
wherein the structural arms define a central opening in the central
area, having positioned therein the lens.
30. An integrated electro-optical package as claimed in claim 28
wherein the structural arms have monolithically formed at the
central area, the lens.
31. A portable electronic device with visual display
comprising:
a portable electronic device having a data output terminal; and
a miniature virtual image display having a viewing aperture, the
miniature virtual image display being operably attached to a
receiver and including an optically transparent substrate having a
major surface with a plurality of light emitting devices formed on
the major surface, each of the light emitting devices having a
first electrode and a second electrode for activating the light
emitting devices, the light emitting devices defining a plurality
of pixels positioned in rows and columns and cooperating to
generate a complete image, when activated, at a central portion of
the major surface, the optically transparent substrate further
having connection pads adjacent outer edges thereof and outside of
the central portion of the major surface with the first electrodes
of the light emitting devices being connected to a first plurality
of the external connection pads defining rows of pixels and the
second electrodes of the light emitting devices being connected to
a second plurality of the external connection pads defining columns
of pixels;
a driver board having a central opening defined therein and having
a first major surface and a second opposed major surface with a
first plurality of connection pads and a second plurality of
connection pads formed on the second opposed major surface, a
plurality of electrical interconnects formed between the first and
second pluralities of connection pads, a plurality of connection
pads formed on the first major surface of the driver board, and a
plurality of electrical interconnects formed between the second
plurality of connection pads formed on the second opposed major
surface of the driver board and the plurality of connection pads
formed on the first major surface of the driver board, the
optically transparent substrate being mounted on the second opposed
major surface of the driver board with the first plurality of
connection pads of the driver board in electrical contact with the
first and second pluralities of external connection pads of the
optically transparent substrate;
a plurality of driver and controller circuits having a plurality of
data input terminals connected to a data output terminal of the
electronic device and further having a plurality of control signal
output terminals adapted to be connected to the first and second
electrodes of the light emitting devices for activating the light
emitting devices to generate images in accordance with data signals
applied to the plurality of data input terminals, the plurality of
driver and controller circuits being mounted on the first major
surface of the driver board with the plurality of control signal
output terminals electrically contacting the plurality of
connection pads on the first major surface of the driver board;
and
a molded carrier ring, having embedded therein a plurality of
leadframes, electrically interfaced with the driver board, the
plurality of light emitting devices and the driver and controller
circuits.
32. A portable electronic device with visual display as claimed in
claim 31 wherein the plurality of light emitting devices on the
major surface of the optically transparent substrate include a
plurality of organic electroluminescent elements on an optically
transparent glass substrate.
33. A portable electronic device with visual display as claimed in
claim 31 further comprised of one of a molded diffractive lens and
a molded refractive lens mounted to the driver board, coextensive
with the complete image generated by the plurality of light
emitting devices, to receive and magnify the complete image and
produce an easily viewable virtual image.
34. A portable electronic device with visual display as claimed in
claim 31 further comprised of at least one of a molded diffractive
lens and a molded refractive lens monolithically formed with the
mounted carrier ring, coextensive with the complete image generated
by the plurality of light emitting devices, to receive and magnify
the complete image and produce an easily viewable virtual
image.
35. A portable electronic device with visual display as claimed in
claim 31 further comprised of at least one of a molded diffractive
lens and a molded refractive lens mounted to the molded carrier
ring, coextensive with the complete image generated by the
plurality of light emitting devices, to receive and magnify the
complete image and produce an easily viewable virtual image.
36. A portable electronic device with visual display as claimed in
claim 31 wherein the portable electronic device includes portable
communications equipment.
37. A portable electronic device with visual display as claimed in
claim 36 wherein the portable communications equipment is one of a
cellular telephone, a two-way radio, a data bank and a pager.
38. A method of fabricating an electro-optical package comprising
the steps of:
forming a plurality of light emitting devices on a major surface of
an optically transparent substrate, each of the plurality of light
emitting devices having first and second electrodes for activating
the light emitting devices, the light emitting devices defining a
plurality of pixels positioned in rows and columns and cooperating
to generate a complete image, when activated, at a central portion
of the major surface, the optically transparent substrate further
being formed with connection pads adjacent outer edges thereof and
outside of the central portion of the major surface with the a
plurality of first electrodes of the light emitting devices being
connected to a first plurality of the external connection pads
defining rows of pixels and a plurality of second electrodes of the
light emitting devices being connected to a second plurality of the
external connection pads defining columns of pixels;
forming a driver board having a central opening defined therein,
with a first major surface and a second opposed major surface and
forming first and second means for electrical connection on the
second opposed major surface with a plurality of electrical
interconnects formed between the first and second means for
electrical connection, and forming a means for electrical
connection on the first major surface of the driver board with a
plurality of electrical interconnects formed between the means for
electrical connection on the first major surface and the first and
second means for electrical connection on the second opposed major
surface;
forming a plurality of driver and controller circuits having a
plurality of data input terminals and further having a plurality of
control signal output terminals adapted to be connected to the
first and second electrodes of the light emitting devices for
activating the light emitting devices to generate the complete
images in accordance with a plurality of data signals applied to
the plurality of data input terminals;
mounting the optically transparent substrate on the second opposed
major surface of the driver board with the first means for
electrical connection of the driver board in electrical contact
with the first and second pluralities of external connection pads
of the optically transparent substrate;
mounting the plurality of driver and controller circuits on the
first major surface of the driver board with the plurality of
control signal output terminals electrically contacting the
plurality of connection pads on the first major surface of the
driver board; and
molding a carrier ring about an outer periphery of the driver
board, having a plurality of embedded leadframes supported therein,
electrically interfaced with the driver board, the light emitting
devices and the plurality of driver and controller circuits.
39. A method of fabricating an electro-optical package as claimed
in claim 38 wherein the step of forming a plurality of light
emitting devices on the major surface of an optically transparent
substrate includes forming a plurality of organic
electroluminescent elements on an optically transparent glass
substrate.
40. A method of fabricating an electro-optical package as claimed
in claim 38 further includes the step of mounting one of a molded
diffractive lens and a molded refractive lens on one of the driver
board and the carrier ring, coextensive with the complete image
generated by the plurality of light emitting devices to receive and
magnify the complete image and produce an easily viewable virtual
image.
41. A method of fabricating an electro-optical package as claimed
in claim 38 further includes the step of monolithically molding one
of a diffractive lens and a refractive lens with the carrier ring,
coextensive with the complete image generated by the plurality of
light emitting devices to receive and magnify the complete image
and produce an easily viewable virtual image.
Description
FIELD OF THE INVENTION
The present invention pertains to packages containing electrical
and optical components connected in cooperation and more
specifically to an integrated electro-optical package having a
carrier ring for electrically connecting optical components and
driver circuits in electrical circuitry.
BACKGROUND OF THE INVENTION
Portable communications transceivers and other portable electronic
equipment, such as cellular and cordless telephones, pagers, data
banks, and the like, are becoming increasingly popular. In some
instances it is possible to send complete messages, including
alpha-numerics and/or graphics by way of novel pagers. Thus,
complete messages can be sent to specific recipients. Through the
use of digital signals that are being transmitted at ever
increasing frequencies, it is possible to transmit increasingly
larger and more complex messages to remote portable units, using
novel devices.
Of greatest importance when utilizing these new novel devices to
transmit and receive information, is the display through which the
information is received. It is desirable to incorporate into these
novel devices an electro-optical package containing electrical and
optical components that are capable of producing a display that is
large enough to be useful, while in keeping with size restrictions
as well as low electrical power needs.
Light emitting devices (LEDs) are useful in various displays and
are utilized in display modules that are incorporated into
electro-optical packages to create an image which is then magnified
to the extent necessary for the user to view the image. LEDs are
especially useful in a new miniature virtual image display that
utilizes a two-dimensional array of LEDs as an image source.
Generally, these two dimensional arrays include large numbers of
light emitting devices, from 5000 to 80,000 or more. A specific
example exists where the image source consists of a high pixel
count 2-dimensional array of LEDs, such as 240 columns by 144 rows,
for a total of 34,560 pixels. An array the size of this specific
example requires a total of 384 external interconnections to
properly scan, or activate, and produce an image thereon. The array
of LEDs is used to form complete images containing pictorial
(graphic) and/or alphanumeric characters. The complete images are
then magnified to produce virtual images which appear to an
operator to be at least the size of a standard sheet of paper.
A major problem facing the productizing of such arrays is the
penalty paid for this very large number of connection, or bond,
pads required to provide information to the array and in the
interfacing of the array with additional components of the
electro-optical package. One specific drawback in the development
of this type of electro-optical packages is the increased
semiconductor chip or chip area required for the connection pads
and the interconnect fanout necessary to connect the connection
pads to the rows and columns. A significant portion of the
projected cost of the semiconductor chip on which the array is
constructed is in the starting material and, with the 240.times.144
example set up for wire bonded external interconnects, the emitting
region (light emitting device array) occupies less than 20% of the
total chip area with the remaining 80% required for connection pads
and interconnect fan out. Conventional direct chip attach (DCA)
bonding will improve this ratio only slightly because of the large
pad sizes and interconnect pitches associated with the current
state-of-the-art.
A large bonding substrate area is also required since a similar pad
and interconnect fanout pattern must be repeated on accompanying
semiconductor chips containing the drive electronics. Furthermore,
the drive chips themselves must be large enough to accommodate the
large number of connection pads (384 in this example).
An additional drawback in the development of electro-optical
packages is the incorporation of an optical magnification system.
Typically an external lens system is applied to magnify the image
generated by the array of LEDs for ease of viewing by the user. The
net result is a large overall package which is not attractive for
the applications of portable electronic devices where a premium is
placed on small physical volumes.
One way to alleviate package size problems in LED display packaging
is to simplify the package and assembly by integrating the driver
board with a molded carrier ring, together capable of supporting a
LED display chip, a plurality of drive chips and a molded lens that
serves as one element of an optical magnifier system. The molded
carrier ring, has embedded therein leadframes, and in combination
with its supporting abilities, aids in minimizing the size
requirement of the electro-optical package and the ability to
interface with a printed circuit board. Included within the
electro-optical package is the incorporation of a plurality of
driver and controller circuits mounted on the driver board, having
data input terminals and further having control signal output
terminals interfaced with a plurality of leads of the light
emitting devices for activating the light emitting devices to
generate images in accordance with data signals applied to the data
input terminals.
In inorganic LED configurations, generally a semiconductor
substrate, or integrated circuit, is mounted on a printed circuit
board or the like and the accepted method for connecting the
substrate to external circuits is to use standard wire bond
technology. However, when a semiconductor substrate having a
relatively large array of electrical components or devices formed
thereon is to be connected, standard wire bond techniques can
become very difficult. For example, if a relatively large array
(greater than, for example, 10,000 or 100.times.100) of light
emitting diodes is formed on a substrate with a pitch
(center-to-center separation) of P, then connection pads on the
perimeter of the substrate will have a 2P pitch. This is true
because every other row and every other column goes to an opposite
edge of the perimeter to increase the distance between the
connection pads as much as possible.
At the present time wire bond interconnects from connection pads
having a pitch of 4.8 mils is the best that is feasible. Thus, in
the array mentioned above of 100.times.100 light emitting devices
the connection pads on the perimeter of the semiconductor chip
would have a minimum pitch of 4.8 mils, with 50 connection pads
situated along each edge of the perimeter. As more devices are
included in the array, more connection pads are required and the
perimeter size to accommodate the additional connection pads
increases at an even greater rate. That is, since the minimum pitch
of the bonding pads is 4.8 mils, the pitch of the devices in the
array can be as large as 2.4 mils, or approximately 61 microns,
without effecting the size of the substrate. Thus, even if the
devices can be fabricated smaller than 61 microns, the minimum
pitch of the bonding pads will not allow the perimeter of the
substrate to be made any smaller. It can quickly be seen that the
size of the substrate is severely limited by the limitations of the
wire bonding technology.
Of greatest concern is time and cost spent in the manufacturing of
electro-optical packages containing electrical components which are
typically interfaced using wire bonding technology, and optical
components which are required for magnification. In addition, there
exist drawbacks in the ease of interfacing the electro-optical
package to a printed circuit board, or the like, or in the overall
ease of handling the completely integrated package.
Thus, there is a need for interconnect and packaging structures and
techniques which can substantially reduce the manufacturing cost
and assembly time for an electro-optical package containing
electrical and optical components connected in electrical
cooperation.
Accordingly, it is highly desirable to provide methods of
fabricating LED arrays and interconnect apparatus packages which
overcome these problems.
It is a purpose of the present invention to provide a new and
improved method of fabricating LED arrays and interconnect
apparatus packages.
It is a further purpose of the present invention to provide a new
and improved LED array and integrated driver circuitry packaging
for driving large arrays of LEDs which includes the use of a molded
carrier ring to support a display chip, a plurality of driver
chips, a driver board, and a molded lens that serves as one element
of an optical magnifier system.
It is a still further purpose of the present invention to provide a
new and improved method of fabricating LED arrays and driver
packaging which provides for a molded carrier ring, that overall is
simpler and more efficient than prior methods and which is easily
adaptable to high production levels.
It is yet another purpose of the present invention to pride a new
and improved electro-optical package and method of fabricating,
which includes simpler construction and assembly than previous
packages, involves lower cost in the manufacturing of the package,
producing a stronger overall unit that includes easier mounting to
a printed circuit board and involves easier overall handling.
SUMMARY OF THE INVENTION
The above problems and others are substantially solved and the
above purposes and others are realized in an integrated
electro-optical package including a molded carrier ring which
serves to support a light emitting device (LED) display chip, a
driver board, a plurality of driver chips, and a molded lens.
The display chip of the present invention is composed of an
optically transparent substrate having a major surface with an
array of light emitting devices formed on the major surface at a
central portion thereof and cooperating to generate a complete
image. Each of the light emitting devices have first and second
electrodes for activating the light emitting devices. The optically
transparent substrate further has a plurality of external
connection/mounting pads adjacent outer edges thereof and outside
of the central portion of the major surface with the first
electrodes of the light emitting devices being connected to a first
plurality of the external connection/mounting pads and the second
electrodes of the being light emitting devices being connected to a
second plurality of the external connection/mounting pads. The
array of LEDs and the contained electrical connections form the LED
display chip, or light emitting device imager (LEDI) chip of the
present invention.
There is provided a driver board having an upper first major
surface and a second opposed major surface, defining a central
opening substantially coextensive with the complete image at the
central portion of the major surface of the optically transparent
substrate. The driver board further has a plurality of electrical
conductors formed thereon as surface mounted leadframes, and/or
patterned electrical interconnects. Each of the plurality of
electrical conductors extends from a connection/mounting pad
adjacent an edge of the central opening on the second opposed major
surface of the driver board, to a connection/mounting pad formed
about a periphery of the second opposed major surface of the driver
board. An additional plurality of electrical conductors, formed as
embedded leadframes or plated through-hole vias, extend from the
plurality of connection/mounting pads formed about the periphery of
the second opposed major surface of the driver board, to a
plurality of connection/mounting pads formed on the upper first
major surface of the driver board.
The optically transparent substrate of the LED display chip can be,
for example, formed of glass or some other suitable transparent
material defining the central portion, and having the array of
light emitting devices formed thereon. The plurality of external
connection/mounting pads of the optically transparent substrate are
positioned to align with the plurality of connection pads adjacent
an edge of the central opening of the driver board. During
assembly, the major surface of the optically transparent substrate
is flip chip bump bonded to the second opposed major surface of the
driver board, substantially coextensive with the central opening
formed in the driver board, with the first and second pluralities
of external connection/mounting pads of the optically transparent
substrate being in electrical contact with the connection/mounting
pads of the driver board. A plurality of driver and controller
circuits are mounted on the upper first major surface of the driver
board and have data input terminals and further have control signal
output terminals connected to the first and second electrodes of
the light emitting devices for activating the light emitting
devices to generate complete images in accordance with data signals
applied to the data input terminals.
In the preferred embodiment the first plurality of external
connection/mounting pads and the second plurality of external
connection/mounting pads of the optically transparent substrate are
bump bonded to the plurality of mounting/connection pads formed
adjacent an edge of the central opening of the driver board to
substantially reduce the allowable pitch of the connection/mounting
pads. Also, the connection pads on the major surface of the driver
board are positioned into a matrix of rows and columns to allow a
substantially greater number of connection pads in a substantially
smaller surface area.
There is provided a molded carrier ring having embedded therein
conductors, such as embedded leadframes, in electrical cooperation
with the driver board and display chip, for external connection of
the electro-optical package to a standard printed circuit board.
The molded carrier ring serves to support the driver board in an
embodiment where the driver board is the main stress member,
supporting the LED display chip, the driver and control circuits,
and a molded lens. Alternatively, the molded carrier ring is formed
having a plurality of structural arms, or rib-like support members,
extending from a periphery of the carrier ring to a central area,
defining a central opening, with the plurality of structural arms
serving to act as stress members by supporting the molded lens
within the central opening formed by the structural arms.
Alternatively, the molded lens may be monolithically formed with
the carrier ring, in the central area defined by the structural
arms. The embedded driver board, in this particular embodiment,
continues to support the LED display chip and the plurality of
driver and control circuits.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features believed characteristic of the invention are set
forth in the claims. The invention itself, however, as well as
other features and advantages thereof will be best understood by
reference to detailed descriptions which follow, when read in
conjunction with the accompanying drawings, wherein:
FIG. 1 is a greatly enlarged view in top plan of a partial array of
light emitting devices formed on an optically transparent
substrate;
FIG. 2 is a simplified cross-sectional view of a single organic
electroluminescent element on a glass substrate;
FIG. 3 is an enlarged view in top plan of a LEDI chip mounted on a
driver board having defined therein a central opening, including a
plurality of electrical connections;
FIG. 4 is a simplified sectional view of the components of an
electro-optical package of the present invention, wherein the
driver board acts as a main stress member in conjunction with the
molded carrier ring, assembled into a complete package;
FIG. 5 is a top view in perspective illustrating the relative
positions of the components of an electro-optical package, similar
to that illustrated in FIG. 4, in accordance with the present
invention;
FIG. 6 is a simplified sectional view of the components of an
electro-optical package of the present invention assembled into a
complete package, wherein the molded carrier ring has extending
therefrom structural arms to support the molded lens;
FIG. 7 is a top view in perspective illustrating the relative
positions of the components of an electro-optical package, similar
to that illustrated in FIG. 6, in accordance with the present
invention;
FIG. 8 is a simplified schematic view of a miniature virtual image
display incorporating the electro-optical package of the present
invention;
FIGS. 9 and 10 are additional simplified schematic views, similar
to FIG. 8, of other miniature virtual image displays incorporating
the electro-optical package of the present invention;
FIGS. 11, 12, and 13 illustrate a front view, side elevational
view, and a top plan, respectively, of an image manifestation
apparatus utilizing the integrated electro-optical package of the
present invention;
FIG. 14 is a 4.times. magnified view in side elevation of the
apparatus of FIG. 11;
FIG. 15 is a view in perspective of a portable communications
receiver incorporating the miniature virtual image display of FIG.
8;
FIG. 16 is a simplified view generally as seen from the line 16--16
of FIG. 15;
FIG. 17 is a view in perspective of another portable communications
receiver incorporating the miniature virtual image display of FIG.
8;
FIG. 18 is a simplified view generally as seen from the line 18--18
of FIG. 17; and
FIG. 19 is a view in perspective illustrating a typical view as
seen by the operator of the portable communications receiver of
FIG. 15.
DESCRIPTION OF THE PREFERRED EMBODIMENT
During the course of this description, like numbers are used to
identify like elements according to the different figures that
illustrate the invention. It should be understood that a wide
variety of light emitting devices, including liquid crystal
displays (LCDs), light emitting diodes (LEDs), vertical cavity
surface emitting lasers (VCSELs), etc., can be utilized, but light
emitting diodes will be utilized throughout the following
description for simplicity. Referring specifically to FIG. 1, a
greatly enlarged view in top plan of an optically transparent
substrate 10 having an array 15 of light emitting devices thereon
is illustrated. For simplicity of illustration, only a
representative portion of optically transparent substrate 10 has
been completed. Optically transparent substrate 10 has a major
surface 11 with a plurality of light emitting devices 12 formed
thereon. Light emitting devices 12 are organic/polymer
electroluminescent elements or light emitting diodes. Hereinafter,
for simplification of this disclosure, the term organic/polymer
will be shortened to "organic". In this embodiment, each light
emitting device 12 defines a pixel, with light emitting devices 12
positioned in rows and columns and cooperating to generate a
complete image, when activated, at a central portion 13 of major
surface 11.
Referring specifically to FIG. 2, a simplified and greatly enlarged
cross-sectional view of a single organic light emitting device 12
on optically transparent substrate 10, which in this embodiment is
an optically transparent glass substrate, is illustrated. Light
emitting device 12 includes a layer 18 of conductive material which
serves as the anode of the device 12 in this specific embodiment.
An organic layer or layers 19/20 includes one or more layers of
polymers or low molecular weight organic compounds. The organic
materials that form the layers are chosen for their combination of
electrical and luminescent properties, and various combinations of
hole transporting, electron transporting, and luminescent materials
can be used. In this embodiment, for example, layer 19 is a hole
transport layer and layer 20 is a luminescent electron transport
layer. A second layer 21 of conductive material is deposited on the
upper surface of layers 19/20 and serves as the cathode in this
specific embodiment. For illustrative purposes, the directional
arrows shown in FIG. 2, are meant to illustrate the direction of
the light emitted by the light emitting devices 12.
Generally, either the anode or the cathode must be optically
transparent to allow the emission of light therethrough. In this
embodiment layer 18 is formed of indium-tin oxide (ITO) which is
optically transparent. In some applications a very thin metal film
may be used as a transparent conductor instead of the ITO. Also, to
reduce the potential required, the cathode is generally formed of a
low work function metal/conductor or combination of
metals/conductors, at least one of which has a low work function.
In this embodiment the cathode is formed of low work function
material, such as heavily doped diamond, or the cathode may be a
conductive metal incorporating cesium, calcium or the like. A
plurality of first electrodes, e.g. the anodes, of light emitting
devices 12 are connected by horizontal electrical conductors 16 to
define rows of pixels, and a plurality of second electrodes, e.g.
the cathodes, of light emitting devices 12, are connected by
vertical electrical conductors 17 to define columns of pixels,
thereby forming a LED display chip 14, or LEDI chip, from an
addressable array 15 of light emitting devices 12.
A list of some possible examples of materials for the organic layer
or layers 19/20 of the above described light emitting device 12
follows. As a single layer of polymer, some examples are:
poly(p-phenylenevinylene) (PPV); poly(p-phenylene) (PPP); and
poly[2-methoxy, 5-(2'-ethylhexoxy)1,4-phenylenevinylene] (MEH-PPV).
As an electron transporting electroluminescent layer between a hole
transporting layer or one of the single layer polymers listed above
and a low work function metal cathode, an example is:
8-hydroxquinoline aluminum (ALQ). As an electron transporting
material, an example is:
2-(4-tert-butylphenyl)-5-(p-biphenylyl)-1,3,4-oxadiazole
(butyl-PBD). As a hole transport material, some examples are:
4,4'-bis[N-phenyl-N-(3-methylphenyl)amino]biphenyl (TPD); and
1,1-bis(4-di-p-tolyaminophenyl)cyclohexane. As an example of a
fluorescent. that may be used as a single layer or as a dopant to
an organic charge transporting layer is coumarin 540, and a wide
variety of fluorescent dyes. Examples of low work function metals
include: Mg:In, Ca, and Mg:Ag.
Light emitting devices 12 are formed on optically transparent
substrate 10 in a central portion 13 of major surface 11 less than
approximately 20 microns in diameter, in the embodiment illustrated
approximately 10 microns in diameter. Also, the pitch, or spacing
between centers of light emitting devices 12, is less than
approximately 30 microns, and in the present embodiment is 20
microns.
In addition to optically transparent substrate 10, a mounting
board, or driver board, is included having a plurality of driver
and control circuits (not shown) mounted on a major surface
thereof. Referring specifically to FIG. 3, an enlarged view in top
plan of LED display chip 14, positioned on a driver board 30 is
illustrated. In the simplest embodiment, driver board 30 is a
separate component, formed of a convenient printed circuit board,
such as FR4 or the like, having an upper first major surface (not
shown) and a second opposed major surface 32. There are positioned
on the upper first major surface of driver board 30 a plurality of
glob top, or overmolded, driver and control circuitry chips (not
shown) which are attached to driver board 30 using wirebonding
technology and/or bump bonding technology. The plurality of driver
and control circuitry chips are composed of driver and control
circuits generally formed as smaller integrated circuits which are
wire bonded or bump bonded to electrical contacts on the first
major surface of driver board 30. Driver board 30 has formed within
a central area, a central opening 33 through which the image
generated by LED display chip 14 passes.
Illustrated in FIG. 3 is the second opposed major surface 32 of
driver board 30 having LED display chip 14 mounted substantially
coextensive with the central opening (not shown) formed through the
first major surface and the second opposed major surface 32 of
driver board 30. Disclosed in the preferred embodiment of driver
board 30 are a plurality of electrical conductors 34, each
extending from a connection/mounting pad 35 on the second opposed
major surface 32 of driver board 30, adjacent an edge of the
central opening (not shown), to a connection/mounting pad 36,
positioned about the outer periphery of driver board 30, to
electrically connect the rows and columns of light emitting devices
12 of LED display chip 14 to connection/mounting pads 36. To
completely distribute electrical conductors 34 and
connection/mounting pads 36 around the periphery of driver board
30, electrical conductors 34 are attached to alternate horizontal
electrical conductors 16 and alternate vertical electrical
conductors 17 of LED display chip 14, as illustrated in FIG. 1.
Thus, the space available between adjacent electrical conductors 34
is 2P, or in this specific embodiment 20 microns.
By fanning out electrical conductors 34, connection/mounting pads
36 can be constructed large enough to provide easy electrical
contact thereto. For example, if array 15 of light emitting devices
12 includes 40,000 devices (e.g., 200.times.200) and each device
includes an area having a 10 micron diameter with a pitch P of 20
microns, then the area of a central opening of driver board 30 will
be less than 0.2 inches on a side. Driver board 30, in this
specific embodiment, is constructed with the central opening
approximately 0.2 inches on a side and an outer periphery of 0.5
inches on a side. Thus, the 200 connection/mounting pads on each
side of the periphery of driver board 30 have approximately 60
microns of pitch available.
Electrical conductors 34 and connection/mounting pads 35 and 36 can
be formed from a plurality of partially embedded pattern electrical
interconnects, surface or embedded copper leads, solder paste
screen print interconnects, gold plated interconnects or metal
evaporation. In addition, sol-gel technology, incorporating the
usual steps of printing, patterning, and fusing can be utilized, as
well as standard thin film metallization in which layers of metal
are deposited by, for example, sputtering. In a typical
metallization system, a first layer of chromium is applied by
sputtering to operate as an adhesive layer on driver board 30. A
second layer of copper is applied over the chromium to provide the
desired electrical conduction and a layer of gold is applied over
the copper to provide a barrier and adhesive layer for further
connections. It should be understood that the metallization can be
either an additive or subtractive method with the patterning and
etching being performed by any of the various methods well known in
the art to provide the desired final structure.
Referring now to FIGS. 4-7, illustrated are two embodiments of an
electro-optical package with a molded carrier ring, referenced here
as 40 and 40' It should be noted that all components of the first
embodiment that are similar to components of the second embodiment,
as well as similar to components illustrated in FIGS. 1 and 3, are
designated with similar numbers, having a prime added to indicate
the different embodiment. Referring specifically to FIG. 4, a
greatly enlarged sectional view, illustrating the relative
positions of the components of an electro-optical package 40 are
illustrated. Referring specifically to FIG. 5, shown in perspective
is the first embodiment of the completely integrated
electro-optical package 40 of the present invention. In the
assembly process, driver board 30 is positioned so that the first
major surface 31 is up and connection/mounting pads 35 on second
opposed major surface 32 are positioned to each contact a
connection pad on LED display chip 14 when driver board 30 and LED
display chip 14 are properly registered, as illustrated in FIG. 4.
Driver board 30 is included as having a plurality of driver and
control circuits 42 mounted on first major surface 31 thereof.
Driver and control circuits 42 generally are formed as smaller
integrated circuits which are wire bonded or bump bonded to
electrical contacts on first major surface 31 of driver board 30.
Driver board 30 is, for example, a convenient printed circuit
board, such as an FR4 board or the like.
LED display chip 14 is bump bonded to driver board 30 using
standard bump bonding technology. In addition, driver and control
circuits 42 are mounted to the first major surface 31 of driver
board 30 using either wire bonding technology or bump bonding
technology. The bumps (if used) mounting the LED display chip 14
and the driver and control circuits 42 are formed of a material
that is a relatively good electrical conductor and which can be at
least partially melted and reset to form a good physical
connection. Material which can be utilized for this purpose
includes gold, copper, solder and especially high temperature
solder, conducting epoxy, etc. A bump height of up to 80 microns
can be formed on a square or round connection/mounting pad with a
20 micron diameter. For smaller pitches, 5 micron diameter copper
bumps with a pitch of 10 microns have been formed with a bump
height of 20 microns. Also, 15 micron diameter gold bumps on a 30
micron pitch have been formed to a height of 30 to 45 microns. Some
compatible metal may improve the assembly procedures, e.g., gold
metallization or gold plating on connection/mounting pads 36 of
driver board 30.
In one fabrication technique, driver board 30 includes gold
connection/mounting pads 35 and 36 and a plurality of connection
pads positioned on a first major surface 31 for the mounting of the
driver and control circuits 42. Connection mounting pads 36 and a
plurality of connection pads positioned on a first major surface 31
of driver board 30 are interfaced using a plurality of plated
through-hole vias 44, and/or embedded leadframes 45. Driver and
control circuits 42 are mounted on the first major surface 31 of
driver board 30, opposite the mounting of LED display chip 14
thereby providing sufficient area for the fan-out of electrical
conductors 34 and connection/mounting pads 36 on the second opposed
major surface of driver board 30. As stated, LED display chip 14
also includes gold connection/mounting pads and is flip chip
thermo-compression bonded to driver board 30.
This invention simplifies the packaging and assembly of the
electro-optical package by integrating LED display chip 14 with
driver board 30, having driver electronics mounted thereon. Driver
board 30 is embedded into a molded carrier ring (discussed
presently) in electrical interface, thereby serving as the main
stress member of the electro-optical package, or alternatively is
embedded into a molded carrier ring having monolithically formed
structural arms, which serve as stress members, in conjunction with
driver board 30, of the electro-optical package. The resulting
package can then be directly mounted to a printed circuit board so
that electronic signals can be interfaced.
As illustrated in FIGS. 4-7, driver board 30 is embedded into a
molded carrier ring 50 defining a peripheral ring structure and
having external electrical interface through an embedded leadframe
51. Embedded leadframe 51 is be configured to interface with an
external printed circuit board (not shown) by forming a plurality
of leadframe legs 52, leadframe pins 54 or mounting bumps 56 (shown
in FIG. 6). In the first embodiment of electro-optical package 40,
driver board 30 is embedded into molded carrier ring 50. Driver
board 30 serves as the main stress member for the package by
supporting the LED display chip 14 and the driver and control
circuits 42, (discussed previously), and by supporting a molded
lens 60 (discussed presently). In that driver board 30 is
manufactured to be very thin and compact, and acts as the sole
supporting member for the various components of electro-optical
package 40, electro-optical package 40 is simple and cost effective
to both manufacture and assemble.
The final element in electro-optical package 40 is lens 60 which is
formed using transfer molding techniques. Lens 60 is designed to
serve as one element of an optical magnifier system that magnifies
the image generated by array 15 of light emitting devices 12 of LED
display chip 14. Lens 60, is preferably an injection molded
refractive lens or an injection molded diffractive lens that is
molded and capable of being snap-fit or epoxy glued into central
opening 33 of driver board 30. In the alternative, it is disclosed
to manufacture molded lens 60 separate and apart from the remainder
of the components of electro-optical package 40, and thereafter
mount it by any convenient means now known in the art, onto the
package.
The interstice between LED display chip 14, driver board 30 and
molded lens 60, mounted thereon is filled with an optically
transparent material 62, which may be any convenient material to
provide support and make electro-optical package 40 a more robust
package. In addition, LED display chip 14 subsequent to the
mounting on driver board 30, has a layer of overmolding 64,
positioned on a side opposite the mounting of LED display chip 14,
to protect LED display chip 14 and further reduce the damage of any
stress exerted on LED display chip 14.
It should be understood that for best results driver board 30 and
optically transparent material 62 should be constructed with
indices of refraction which are as close together as practical. If,
for example, the index of refraction of driver board 30 and
optically transparent material 62 differs substantially there is a
tendency for light to reflect back from optically transparent
substrate 10 and the efficiency of electro-optical package 40 is
reduced. Generally, an index of refraction of approximately 1.5 for
driver board 30 and optically transparent material 62 has been
found to be acceptable.
In addition, an optically transparent substrate of glass or the
like, such as optically transparent substrate 10, has the added
advantage of providing additional environmental protection for
array 15 of light emitting devices 12. In that transparent
material, such as glass and the like can be provided which has a
coefficient of thermal expansion which is the same as, or very
close to, the coefficient of thermal expansion of the driver board
30, substantial improvements in thermal cycling life are achieved
with this package.
Referring now to FIGS. 6 and 7, illustrated is a second embodiment
of electro-optical package 40, referenced here as 40'. Again, it
should be noted that all components of the first embodiment that
are similar to components of the second embodiment, as well as
similar to components illustrated in FIGS. 1 and 3, are designated
with similar numbers, having a prime added to indicate the
different embodiment. Electro-optical package 40', like
electro-optical package 40, is composed of a LED display chip 14',
bump bonded to a driver board 30', such as a FR4 board or the like,
having defined therein a central opening 33', through which a
complete image generated by the array 15' of light emitting devices
12' of LED display chip 14' passes. Driver board 30', having a
first major surface 31' and a second opposed major surface 32', has
formed therein a plurality of electrical interconnects, namely a
plurality of plated through-hole vias 44' and/or a plurality of
embedded leadframes 45', to electrically connect the plurality of
connection pads 36', positioned about a periphery of driver board
30', to a plurality of driver and control circuits 42' mounted on a
second opposed major surface 32' of driver board 30'. Molded
carrier ring 50' in this embodiment of electro-optical package 40'
is molded to form a plurality of structural arms 58 which serve in
addition to driver board 30', as the main stress members of
electro-optical package 40'. Structural arms 58 are monolithically
molded as part of carrier ring 50' and project toward a central
area, as shown in FIG. 7, thereby defining a central opening 59. As
disclosed in the first embodiment, molded lens 60' is formed to
snap-fit mount or epoxy glue mount into the central opening 59
defined by the plurality of structural arms 58, substantially
coextensive with central opening 33' of driver board 30' and the
complete image generated by the array 15' of light emitting devices
12'. In the alternative, molded lens 60' can be monolithically
molded with molded carrier ring 50' and structural arms 58 at the
time of formation.
Driver board 30' is interfaced with a external printed circuit
board (not shown) using a plurality of embedded leadframes 51',
that are configured to have a plurality of leadframe legs (not
shown), a plurality of leadframe pins (not shown), as illustrated
in FIGS. 4 and 5, or a plurality of mounting bumps 56, as
illustrated in FIGS. 6 and 7. As in the formation of
electro-optical package 40, electro-optical package 40' has a layer
of optically transparent material 62' positioned within an area
formed by the mounting of the various components, and a protective
overmolding 64', positioned to overmold LED display chip 14',
serving as a protective covering and to reduce any stress exerted
on LED display chip 14'.
With regard to the disclosed embodiments, it should be understood
that the image generated by the array of light emitting devices 12
on optically transparent substrate 10 is too small to properly
perceive (fully understand) with the human eye and generally
requires a magnification of at least 10.times. for comfortable and
complete viewing. Lens 60 can be formed as a single lens with
additional optical magnification supplied by an external system or
lens 60 can be formed as a complete magnification system. Several
examples of optical magnification systems which may be incorporated
into lens 60 or applied externally thereto are illustrated in FIGS.
8 through 10, explained below.
Referring to FIG. 8, a miniature virtual image display 70 is
illustrated in a simplified schematic view. Miniature virtual image
display 70 includes image generation apparatus 71, similar to
electro-optical packages 40 and 40' described above, for providing
an image on a surface 72. An optical system, represented by lens
system 73, is positioned in spaced relation to surface 72 of
miniature virtual image display 70 and produces an easily viewable
virtual image viewable by an eye 74 spaced from an aperture 75
defined by lens system 73. As technology reduces the size of the
electro-optical package and/or the light generating devices
contained within, greater magnification and smaller lens systems
are required.
Lens system 73, represented schematically by a single lens, is
mounted in spaced relation from surface 72 so as to receive the
image from surface 72 and magnify it an additional predetermined
amount. It will of course be understood that lens system 73 may be
adjustable for focus and additional magnification, if desired, or
may be fixed in a housing for simplicity.
Eye relief is the distance that eye 74 can be positioned from
viewing aperture 75 and still properly view the image, which
distance is denoted by "d" in FIG. 8. Because of the size of lens
system 73, eye relief, or the distance d, is sufficient to provide
comfortable viewing and in the present embodiment is great enough
to allow a viewer to wear normal eyeglasses, if desired. Because of
the improved eye relief the operator can wear normal corrective
lenses (personal eyeglasses), and the complexity of focusing and
other adjustable features can be reduced, therefore, simplifying
the construction of miniature virtual image display 70.
Referring to FIG. 9, another miniature virtual image display is
illustrated in a simplified schematic. In waveguide virtual image
display 80, image generation apparatus 81, similar to
electro-optical packages 40 and 40' described above, is affixed to
the inlet of an optical waveguide 82 for providing an image
thereto. Optical waveguide 82 is formed generally in the shape of a
parallelogram (side view) with opposite sides, 83, 84 and 85, 86,
equal and parallel but not perpendicular to adjacent sides. Side 83
defines the inlet and directs light rays from the image at image
generation apparatus 81 onto a predetermined area on adjacent side
85 generally along an optical path defined by all four sides. Three
diffractive lenses 87, 88 and 89 are positioned along adjacent
sides 85, 84 and 86, respectively, at three predetermined areas and
the magnified virtual image is viewable at an outlet in side 86.
This particular embodiment illustrates a display in which the
overall size is reduced somewhat and the amount of material in the
waveguide is reduced to reduce weight and material utilized.
Referring to FIG. 10, another specific miniature virtual image
display is illustrated in a simplified schematic. In waveguide
virtual image display 90 an optical waveguide 91 having a generally
triangular shape in side elevation is utilized. Image generation
apparatus 92, similar to electro-optical packages 40 and 40'
described above, for producing an image, is affixed to a first side
93 of optical waveguide 91 and emanates light rays which travel
along an optical path directly to a diffractive lens 94 affixed to
a second side 95. Light rays are reflected from lens 94 to a
diffractive lens 96 mounted on a third side 97. Diffractive lens 96
in turn reflects the light rays through a final refractive lens 98
affixed to the outlet of optical waveguide 91 in side 93, which
refractive lens 98 defines a viewing aperture for waveguide virtual
image display 90. In this particular embodiment the sides of
waveguide virtual image display 90 are angularly positioned
relative to each other so that light rays enter and leave the inlet
and outlet, respectively, perpendicular thereto.
Referring now to FIGS. 11, 12 and 13, another miniature virtual
image display 100 in accordance with the present invention, is
illustrated in a front view, side elevational view, and top plan,
respectively. FIGS. 11, 12 and 13 illustrate miniature virtual
image display 100 approximately the actual size to provide an
indication as to the extent of the reduction in size achieved by
the present invention. Miniature virtual image display 100 includes
an integrated electro-optical package 102, generally similar to
packages, 40 and 40', which includes, in this specific embodiment,
144 pixels by 240 pixels. Each pixel is fabricated approximately 20
microns on a side with a center-to-center spacing between adjacent
pixels of no more than 20 microns. In a preferred embodiment,
integrated electro-optical package 102 produces a luminance less
than approximately 15 fL. This very low luminance is possible
because miniature virtual image display 100 produces a virtual
image. Integrated electro-optical package 102 is mounted onto lens
system 104, which magnifies the image approximately 15.times. to
produce a virtual image approximately the size of an 8.5".times.11"
sheet of paper.
Here is should be noted that because integrated electro-optical
package 102 is very small and the fact that a virtual image is
utilized, rather than a direct view display, the overall physical
dimensions of miniature virtual image display 100 are approximately
1.5 inches (3.8 cm) wide by 0.75 inches (1.8 cm) high by 1.75
inches (4.6 cm) deep, or a total volume of approximately 2 cubic
inches (32 cm.sup.3).
Referring specifically to FIG. 14, a 4.times. magnified view in
side elevation of miniature virtual image display 100 of FIG. 11 is
illustrated for clarity. From this view it can be seen that an air
gap exists between the upper surface of a lens 105 (generally
similar to lens 60 of the present invention) and an optical prism
108. Optical prism 108 is mounted to reflect the image from a
surface 110 and from there through a refractive surface 112. The
image is then directed to an optical lens 114 having a refractive
inlet surface 115 and a refractive outlet surface 116. From optical
lens 114 the image is directed to an optical lens 118 having an
refractive inlet surface 119 and an refractive outlet surface 120.
Also, in this embodiment at least one diffractive optical element
is provided on one of the surfaces, e.g. surface 110 and/or
refractive inlet surface 115, to correct for chromatic and other
aberrations. The operator looks into refractive outlet surface 120
of optical lens 118 and sees a large, easily discernible virtual
image which appears to be behind miniature virtual image display
100.
FIG. 15, illustrates an example of a portable electronic device,
namely a portable communications receiver 130, having a hand held
microphone 131 with a miniature virtual image display 132 mounted
therein. It will of course be understood that portable
communications receiver 130 can be any of the well known portable
receivers, such as a cellular or cordless telephone, a two-way
radio, a pager, a data bank, etc. In the present embodiment, for
purposes of explanation only, portable communications receiver 130
is a portable two-way police radio, generally the type carried by
police officers on duty or security guards. Portable communications
receiver 130 includes a control panel 134 for initiating calls and
a standard visual display 136, if desired, for indicating the
number called or the number calling. Hand held microphone 131 has a
push-to-talk switch 138 and a voice pick-up 140.
Referring to FIG. 16, a simplified sectional view of hand held
microphone 131, as seen from the line 16--16 of FIG. 15, is
illustrated. Miniature virtual image display 132 includes an
electro-optical package, similar to electro-optical packages 40 and
40', described above, having image generation apparatus 141 for
providing an image to a fixed optical system 142, which in turn
produces a virtual image viewable by the operator through an
aperture 144. Fixed optical system 142 is constructed to magnify
the entire image from image generation apparatus 141, without
utilizing moving parts, so that the virtual image viewable through
aperture 144 is a complete frame, or picture, which appears to be
very large (generally the size of a printed page) and is easily
discernible by the operator. The entire electro-optical package is
relatively small and adds virtually no additional space
requirements to hand held microphone 131. Optical system 142 is
constructed with no moving parts, other than optional features such
as focusing, zoom lenses, etc. Further, image generation apparatus
141 requires very little electrical power to generate the image
and, therefore, adds very little to the power requirements of
portable communications receiver 130.
Referring specifically to FIGS. 17 and 18, a second embodiment of a
specific type of portable communications equipment is illustrated
wherein parts similar to those described in relation to FIGS. 15
and 16 are designated with similar numbers with a prime added to
the numbers to indicate a different embodiment. In this embodiment,
a portable communications receiver 130' has a miniature virtual
image display 132' included in the body thereof, instead of in a
hand held microphone. A hand held microphone is optional and this
specific embodiment is desirable for instances where a hand held
microphone is not utilized or not available or for use in pagers
and the like which do not transmit. Miniature virtual image display
132' is basically similar to miniature virtual image display 132 of
FIGS. 15 and 16 and adds very little to the size, weight, or power
consumption of portable communications receiver 130'.
FIG. 19 is a perspective view of hand held microphone 131 of FIGS.
15 and 16, illustrating a typical view 150 seen by an operator
looking into viewing aperture 152 of miniature virtual image
display 132, described in conjunction with FIGS. 15-18. View 150
could be, for example, a floor plan of a building about to be
entered by the operator (a policeman). In operation, the floor plan
is on file at the police station and, when assistance is requested
by the policeman, the station simply transmits video representative
of the previously recorded plan. Similarly, miniature virtual image
display 132 might be utilized to transmit pictures of missing
persons or wanted criminals, maps, extremely long messages, etc.
Many other variations, such as silent receiver operation wherein
the message appears on miniature virtual image display 132 instead
of audibly, are possible.
It should be noted that in the prior art, pagers and other small
receivers in which visual displays are desired, are especially
handicapped by the size of the displays. Generally such displays
are limited to a single short line of text or several digits, and
the size of the display still dictates the size of the receiver.
Further, the display is clearer and easier to read and, because it
utilizes a virtual display, requires very little power for the
operation thereof. In fact, the present display utilizing the
electro-optical package of the present invention uses much less
power than any of the direct view displays normally utilized in
electronic equipment and, as a result, can be fabricated in much
smaller sizes.
Thus, the present invention illustrates and teaches integrated
electro-optical packages having a display chip, a driver board, a
molded carrier ring and at least one molded optical component, that
are not limited in size by the electrical connections and the
optics and which are substantially smaller than previous integrated
packages which perform the same functions. Also, the present
invention illustrates and teaches an integrated electro-optical
package which contains an array of light generating devices formed
on a substrate, mounted on a driver board, which is electrically
interfaced with a molded carrier ring. The driver board having a
central opening defined therein, in combination with optical
elements mounted either directly thereon, monolithically formed
with the molded carrier ring, or positioned within a central
portion of a plurality of structural arms of the molded carrier
ring so as to create a generally compact and cost effective
electro-optical package to manufacture.
While we have shown and described specific embodiments of the
present invention, further modifications and improvements will
occur to those skilled in the art. We desire it to be understood,
therefore, that this invention is not limited to the particular
forms shown and we intend in the appended claims to cover all
modifications that do not depart from the spirit and scope of this
invention.
* * * * *